v2.7.1348

Default to 2026-01 Contest API

The 2.6 release supported the 2023-06 Contest API spec. As much of the (then draft)
2026-01 API was already supported as well - basically anything that wasn't a breaking
change. If you wanted to try the breaking changes as well you could set the
ICPC_CONTEST_API system property to 'draft'.

The 2.7 release will support 2026-01 by default and ICPC_CONTEST_API will be used to
enable any future spec. This change integrates the breaking changes:
- contest penalty time and scoreboard times update to RELTIME
- clarifications allow multiple teams and groups
- update api info to correct version
- updates the readme to the correct spec versions